For example, in a data service system including a data server or provider and users to whom data are served from the data server, the user is charged proportionally to an amount of data served to the user or on a flat-rate basis not depending upon the served data amount, for example.
Also, there is disclosed in the U.S. Pat. No. 6,041,316 a network system in which low-quality data are normally served but the user can be served with higher-quality data with having to pay an additional charge for the higher quality.
Also, the Japanese Published Unexamined Application No. 164552 of 1998 discloses a video-on-demand transmitter and terminal which make it possible to serve a video program whose quality meets the user's demand and charge the user on a program-quality basis. In the video-on-demand transmitter and terminal disclosed in this Japanese Published Unexamined Application, there is used a data processing algorithm such as MPEG-1 or MPEG-2 (these are similar to each other) upon which the quality of a served video program depends and thus the charge for a served video program is varied depending upon whether or not the served video program is a one compressed with MPEG-1 or MPEG-2. For example, MPEG-1 is used at the transmitter while MPEG-2 is used at the terminal.
Namely, in the above Japanese Published Unexamined Application, the charge to the user is varied depending upon the function of the application layer in the video-on-demand transmitter and terminal such as the signal processing technique used for data served to the user.
The above transmitter and terminal has a function to record/reproduce a hardware control layer function such as power supply to the internal circuit in them, but there is not disclosed any system with which the user can selectively grade up the functions of the hardware control layer.
With the above technique, however, a signal processing technique designated by the user once will be fixed and the quality of video program and signal processing will not be selectable even if the state of transmission is changed. Namely, any optimum service will not be available to the user.